1. Field of the Invention
The present invention relates to a probe apparatus, and more particularly, to a probe apparatus for examining the electrical properties of a semiconductor device having a large number of electrode pads, such as ICs.
2. Description of the Related Art
As the integration density of ICs increases to 4 M, 16 M, . . . , the pitch between electrode pads of each IC chip becomes very narrow. With use of a conventional probe card stylus, it is hard to examine ICs whose electrode pads are arranged at pitches as narrow as 100 .mu.m, for example. More specifically, it is difficult to examine an IC chip with narrow-pitch electrode pads by means of a conventional slice stylus, such as a tungsten stylus, whose tip end is limited in machining accuracy. Also, it is very difficult to manufacture a probe apparatus which can examine the IC chip by means of the slice stylus.
Thereupon, a method for manufacturing a quartz probe has been proposed (see Japanese Patent Application No. 1-22085). In this method, which uses the etching process as a typical IC manufacturing technique, quartz is used as the material of probes. This is a selective etching method which is based on the etching anisotropy of crystal axes, that is, the fact that the etching rate of the quartz varies with the directions of the crystal axes X (optical axis), Y (electrical axis), and Z (chemical axis) (X:Y:Z=1:6 or less:100) According to this method, a quartz probe having a probe column pattern thereon is manufactured from a filmy quartz substrate.
In this method, the quartz is cut out along the direction perpendicular to its Z axis to produce a rectangular thin quartz plate 100 whose sides extend parallel to the X or Y axis, as shown in FIG. 10, for example. The quartz plate 100 is etched to form probe columns 103A, 103B, 103C and 103D which correspond to electrode pad columns 102A, 102B, 102C and 102D, respectively, formed individually along the four sides of an IC chip 101. In this case, the Y-axis direction is the longitudinal direction of the probe columns 103A and 103B, while the X-axis direction is the longitudinal direction of the probe columns 103C and 103D.
As a result of trial mass production of probe cards, however, it was indicated that electrical connection with the electrode pads sometimes may be unreliable during the examination according to the method described above. As mentioned before, the etching rate with respect to the X-axis direction is about six times as high as that with respect to the Y-direction. Although the probe columns 103A and 103B, whose longitudinal direction is an alignment with the Y-axis direction, are formed satisfactorily, therefore, the probe columns 103C and 103D, whose longitudinal direction is an alignment with the X-axis direction, are formed having undercut (side etching) portions 111 on the flank of each probe 110, as shown in FIG. 11. These undercut portions are as deep as about 6 .mu.m. Since the individual probes tend to be made thinner and thinner, in order to increase the integration density of the ICs, the undercut is fatal to the probes.